View Full Version : 2 sets of f-stops

Louie Devincentis
4-Apr-2012, 17:53
Hi Gang.
I used the Sinar for the first time today and I noticed that my Rodenstock Sironar 135mm f-5.6 lens has 2 lines of f-stops numbers. The first line reads f-135mm 5.6, 8, 11, 16, 22, 32, 45, 64 these numbers are in white. The second row of numbers are in yellow and read f-400 16, 22, 32, 45, 64. Can anybody enlighten me on the meaning of these numbers.

4-Apr-2012, 18:10
convertible lens I believe.

David Lindquist
4-Apr-2012, 19:47
Yes, that what vinny said. The first version of the Sironar was sold as a convertible in that the front component could be used alone giving a focal length "of about three times the original focal length", to quote a 1968 Rodenstock brochure I have. A 1976 Rodenstock sheet I have gives the optimum aperture of the single (front) component as "between f/45 and f/64." Contrary to usual practice with a convertible lens where the single component is placed behind the diaphragm, Rodenstock indicated the front component was left in front when used by itself.